1. Field of the Invention
The present invention relates to a method and apparatus for storing data in a storage medium. More specifically, the present invention relates to gain and timing control in storing data in a storage medium.
2. Description of the Related Art
In data recording systems, a data drive writes positive and negative “flux transitions” to the medium. A “one” bit (“1”) represents a peak or trough in the signal while a “zero” bit (“0”) indicates that no signal is present. These flux transitions within a data stream can be used to provide feedback for timing and gain control loops. However, if a string of zeros exist for too long, a phase change may not be detected, causing errors in the recording system. This problem can be avoided if the data is encoded so that a “1” is guaranteed to occur at a definite minimum frequency. This is the purpose of modulation coding subject to a classical runlength limited k-constraint.
But there may be advantages to using timing marks or gain control marks other than the symbol “1.” In the 1999 publication “One-Pairs Codes for Partial Response Magnetic Recording,” IEEE Transactions on Magnetics, Vol. 35, No. 3, May 1999, the use of a pair of 1s (i.e. “11”) is described to perform timing recovery for readback of information stored on magnetic recording media in a partial response channel. Still other channel models may benefit from a different encoding system to provide additional features, but the systems are limited to the available control marks and coding blocks in the prior art.
Thus, there is a need in the art to provide more sophisticated timing and gain control marks and/or improved coding algorithms for encoding and storing data in a storage medium.